H3C S7500E Series Ethernet Switches Operation Manual

Operation Manual – MSTP
H3C S7500E Series Ethernet Switches Chapter 1 MSTP Configuration
1-8
Device Comparison process
BPDU of port
after
comparison
z Port BP1 receives the configuration BPDU of
Device A {0, 0, 0, AP1}. Device B finds that the
received configuration BPDU is superior to the
configuration BPDU of the local port {1, 0, 1, BP1},
and updates the configuration BPDU of BP1.
z Port BP2 receives the configuration BPDU of
Device C {2, 0, 2, CP2}. Device B finds that the
configuration BPDU of the local port {1, 0, 1, BP2} is
superior to the received configuration BPDU, and
discards the received configuration BPDU.
BP1: {0, 0, 0,
AP1}
BP2: {1, 0, 1,
BP2}
Device B
z Device B compares the configuration BPDUs of all
its ports, and determines that the configuration
BPDU of BP1 is the optimum configuration BPDU.
Then, it uses BP1 as the root port, the configuration
BPDUs of which will not be changed.
z Based on the configuration BPDU of BP1 and the
path cost of the root port (5), Device B calculates a
designated port configuration BPDU for BP2 {0, 5,
1, BP2}.
z Device B compares the calculated configuration
BPDU {0, 5, 1, BP2} with the configuration BPDU of
BP2. If the calculated BPDU is superior, BP2 will
act as the designated port, and the configuration
BPDU on this port will be replaced with the
calculated configuration BPDU, which will be sent
out periodically.
Root port BP1:
{0, 0, 0, AP1}
Designated
port BP2:
{0, 5, 1, BP2}